New South Basin Groundwater Wells Will Monitor Contamination

Nearly half of 23 monitoring wells planned for the Orange County Water District (OCWD; the District) South Basin groundwater contamination remedial investigation have been constructed. The project is due for completion at the end of August 2017.

The wells are being built at six locations within Irvine and Santa Ana. The need for the wells was identified by the District’s hydrogeologic consultant, Hargis & Associates, who found data gaps where no wells exist to determine the extent of the contamination. These wells will help to fill those data gaps and allow the District to measure groundwater levels and collect water samples to monitor trends in chemical concentrations.

This work is being conducted on a voluntarily basis and is being done in conformance with the National Contingency Plan as required by OCWD board policy. It is consistent with the District’s mission to protect and improve the quality of the groundwater used to supply 75 percent of the total water demand of 2.4 million people in north and central Orange County.

The wells will provide detailed information on the geologic pathways, such as sands, through which contaminated groundwater can flow. Being able to map out these underground flow paths and to periodically collect water samples at specific depths are important parts of the remedial investigation.

Once the remedial investigation (RI) is completed, the District and its consultant will conduct a feasibility study (FS) covering various remediation alternatives. The RI/FS process takes more than a year to complete and is open and transparent with considerable opportunity for public input.

The RI/FS is a well-coordinated, united effort with regional and state environmental regulatory agencies including the Department of Toxic Substances Control and the Regional Water Quality Control Board. These two state agencies are working closely with OCWD and some cooperative potentially responsible parties to map the occurrence of the contaminants, identify appropriate remedies and implement groundwater cleanup. The State Water Resources Control Board is also participating in the project by providing $1 million toward the effort through the Proposition 1 grant funding program.

Groundwater contamination can take decades to clean up, so the District expects to be measuring groundwater levels and collecting water samples from these wells for many years to come.

The new monitoring wells are part of OCWD’s continued dedication to ensure a clean and reliable water supply that protects ratepayers and long-term property values.